100 research outputs found
Kinetic Energy Release Distributions for Câșâ Emission from Multiply Charged Cââ and Cââ Fullerenes
We present asystematic study of experimental kinetic energy release distributions for the asymmetric fission processes Cq+60 C(iq-1\u3c)+70+ C+2 and C q+70 C(q-1)+60+ C+ 2 for mother ions incharge states q 4-8 produced incollisions with slow highly charged ions. Somewhat to our surprise, we find that the KERD for asymmetric fission from Cq+60 are considerably wider and have larger most likely values than the Cq+70 distributions inthe corresponding charge states when q \u3e 4
Two-Center Interference in p-H2 Electron-Transfer Collisions
We report on measurements of transfer excitation in collisions of 0.3-1.3 MeV protons with spatially oriented H2 molecules. Evidences of two center interference are found in the angular distribution of the molecule after a transfer excitation process and directly in the projectile angular scattering distributions. These features can be explained in a way which is analogous to that for the interferences in Young\u27s classical double slit experiment: The fast projectiles preferentially capture electrons close to either of the molecular nuclei, and thereby they change their momenta and de Broglie wavelengths. The waves emerging from the two \u27slits\u27 of the molecule interfere yielding the observed interference structure
Evidence of Wave-Particle Duality for Single Fast Hydrogen Atoms
We report the direct observation of interference effects in a Young\u27s double-slit experiment where the interfering waves are two spatially separated components of the de Broglie wave of single 1.3 MeV hydrogen atoms formed close to either target nucleus in H++H2 electron-transfer collisions. Quantum interference strongly influences the results even though the hydrogen atoms have a de Broglie wavelength, λdB, as small as 25 fm
Kinetic-Energy-Release Distributions and Barrier Heights for Cââș Emission from Multiply Charged Cââ and Cââ Fullerenes
We present experimental kinetic-energy-release distributions in the asymmetric fission processes C60q+ â C58 (q-1)+ + C2+ and C70q+ â C68 (q-1)+ + C2+ for highly excited mother ions in charge states q=4-8. We find that the distributions for C70q+ are considerably narrower and peak at lower energies than for C60q+ in the corresponding charge state when q\u3e4. Further, semiempirical values for C2+ fission barrier heights were extracted for q=4-6 by means of a statistical approach and the measured intensity ratios between fission and C2 evaporation
Importance of Thomas Single-Electron Transfer in Fast p-He Collisions
We report experimental angular differential cross sections for nonradiative single-electron capture in p-He collisions (p+ He â H + He+) with a separate peak at the 0.47 mrad Thomas scattering angle for energies in the 1.3-12.5 MeV range. We find that the intensity of this peak scales with the projectile velocity as vP-11. This constitutes the first experimental test of the prediction from 1927 by L. H. Thomas [Proc. R. Soc. 114, 561 (1927)]. At our highest energy, the peak at the Thomas angle contributes with 13.5% to the total integrated nonradiative single-electron capture cross section
Multiplicity dependence of light (anti-)nuclei production in pâPb collisions at sNN=5.02 TeV
The measurement of the deuteron and anti-deuteron production in the rapidity range â1 < y < 0 as a function of transverse momentum and event multiplicity in pâPb collisions at âsNN = 5.02 TeV is presented. (Anti-)deuterons are identified via their specific energy loss dE/dx and via their time-of- flight. Their production in pâPb collisions is compared to pp and PbâPb collisions and is discussed within the context of thermal and coalescence models. The ratio of integrated yields of deuterons to protons (d/p) shows a significant increase as a function of the charged-particle multiplicity of the event starting from values similar to those observed in pp collisions at low multiplicities and approaching those observed in PbâPb collisions at high multiplicities. The mean transverse particle momenta are extracted from the deuteron spectra and the values are similar to those obtained for p and particles. Thus, deuteron spectra do not follow mass ordering. This behaviour is in contrast to the trend observed for non-composite particles in pâPb collisions. In addition, the production of the rare 3He and 3He nuclei has been studied. The spectrum corresponding to all non-single diffractive p-Pb collisions is obtained in the rapidity window â1 < y < 0 and the pT-integrated yield dN/dy is extracted. It is found that the yields of protons, deuterons, and 3He, normalised by the spin degeneracy factor, follow an exponential decrease with mass number
Global polarization of hyperons in Pb-Pb collisions at = 2.76 and 5.02 TeV
International audienceThe global polarization of the and hyperons is measured for Pb-Pb collisions at = 2.76 and 5.02 TeV recorded with the ALICE at the LHC. The results are reported differentially as a function of collision centrality and hyperon's transverse momentum () for the range of centrality 5-50%, GeV/, and rapidity . The hyperon global polarization averaged for Pb-Pb collisions at = 2.76 and 5.02 TeV is found to be consistent with zero, (%) 0.01 0.06 (stat.) 0.03 (syst.) in the collision centrality range 15-50%, where the largest signal is expected. The results are compatible with expectations based on an extrapolation from measurements at lower collision energies at RHIC, hydrodynamical model calculations, and empirical estimates based on collision energy dependence of directed flow, all of which predict the global polarization values at LHC energies of the order of 0.01%
Measurement of K(892) production in inelastic pp collisions at the LHC
International audienceThe first results on Kâ(892)± resonance production in inelastic pp collisions at LHC energies of s=5.02, 8, and 13 TeV are presented. The Kâ(892)± has been reconstructed via its hadronic decay channel Kâ(892)â±KS0+ϱ with the ALICE detector. Measurements of transverse momentum distributions, pT-integrated yields, and mean transverse momenta for charged Kâ(892) are found to be consistent with previous ALICE measurements for neutral Kâ(892) within uncertainties. For pT>1 GeV/c the Kâ(892)± transverse momentum spectra become harder with increasing centre-of-mass energy from 5.02 to 13 TeV, similar to what previously observed for charged kaons and pions. For pT<1 GeV/c the Kâ(892)± yield does not evolve significantly and the abundance of Kâ(892)± relative to K is rather independent of the collision energy. The transverse momentum spectra, measured for Kâ(892)± at midrapidity in the interval 0 <pT<15 GeV/c, are not well described by predictions of different versions of PYTHIA 6, PYTHIA 8 and EPOS-LHC event generators. These generators reproduce the measured pT-integrated Kâ±/K ratios and describe well the momentum dependence for pT<2 GeV/c
Non-linear flow modes of identified particles in Pb-Pb collisions at = 5.02 TeV
The -differential non-linear flow modes, , , and for , , , p + , + and -meson have been measured for the first time at = 5.02 TeV in Pb-Pb collisions with the ALICE detector at the Large Hadron Collider. The results were obtained with a multi-particle technique, correlating the identified hadrons with reference charged particles from a different pseudorapidity region. These non-linear observables probe the contribution from the second and third order initial spatial anisotropy coefficients to higher flow harmonics. All the characteristic features observed in previous -differential anisotropic flow measurements for various particle species are also present in the non-linear flow modes, i.e. increase of magnitude with increasing centrality percentile, mass ordering at low and particle type grouping in the intermediate range. Hydrodynamical calculations (iEBE-VISHNU) that use different initial conditions and values of shear and bulk viscosity to entropy density ratios are confronted with the data at low transverse momenta. These calculations exhibit a better agreement with the anisotropic flow coefficients than the non-linear flow modes. These observations indicate that non-linear flow modes can provide additional discriminatory power in the study of initial conditions as well as new stringent constraints to hydrodynamical calculations.The p-differential non-linear flow modes, v, v, v and v for Ï, K, , p + , Î + and Ï-meson have been measured for the first time at = 5.02 TeV in Pb-Pb collisions with the ALICE detector at the Large Hadron Collider. The results were obtained with a multi-particle technique, correlating the identified hadrons with reference charged particles from a different pseudorapidity region. These non-linear observables probe the contribution from the second and third order initial spatial anisotropy coefficients to higher flow harmonics. All the characteristic features observed in previous p-differential anisotropic flow measurements for various particle species are also present in the non-linear flow modes, i.e. increase of magnitude with increasing centrality percentile, mass ordering at low p and particle type grouping in the intermediate p range. Hydrodynamical calculations (iEBE-VISHNU) that use different initial conditions and values of shear and bulk viscosity to entropy density ratios are confronted with the data at low transverse momenta. These calculations exhibit a better agreement with the anisotropic flow coefficients than the non-linear flow modes. These observations indicate that non-linear flow modes can provide additional discriminatory power in the study of initial conditions as well as new stringent constraints to hydrodynamical calculations.[graphic not available: see fulltext]The -differential non-linear flow modes, , , and for , , , p + , + and -meson have been measured for the first time at = 5.02 TeV in Pb-Pb collisions with the ALICE detector at the Large Hadron Collider. The results were obtained with a multi-particle technique, correlating the identified hadrons with reference charged particles from a different pseudorapidity region. These non-linear observables probe the contribution from the second and third order initial spatial anisotropy coefficients to higher flow harmonics. All the characteristic features observed in previous -differential anisotropic flow measurements for various particle species are also present in the non-linear flow modes, i.e. increase of magnitude with increasing centrality percentile, mass ordering at low and particle type grouping in the intermediate range. Hydrodynamical calculations (iEBE-VISHNU) that use different initial conditions and values of shear and bulk viscosity to entropy density ratios are confronted with the data at low transverse momenta. These calculations exhibit a better agreement with the anisotropic flow coefficients than the non-linear flow modes. These observations indicate that non-linear flow modes can provide additional discriminatory power in the study of initial conditions as well as new stringent constraints to hydrodynamical calculations
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